Eleven new sunspot groups emerged over the past week, August 10 – 16, 2023, but average solar indicators declined.

There were two new sunspot groups on August 11, three more on

August 13, another on August 14, two more on August 15, and three more on August 16.

The average daily sunspot numbers declined from 108.9 to 95.7, while the average daily solar flux dropped from 166.4 to 154.2.

Predicted solar flux is 160 on August 17 – 24; 162, 160, and 164 on August 25 – 27; 168 on August 28 – 31; 165, 163, and 160 on September 1 – 3; 158, 155, 152, and 150 on September 4 – 7; 148, 142, 140, and 130 on September 8 – 11; 135 on September 12 – 14, and 145, 150, and 155 on September 15 – 17.

Predicted planetary A index is 15, 12, and 8 on August 17 – 19; 5 on August 20 – 25; 12 on August 26; 5 on August 27 through September 5; 10, 8, and 8 on September 6 – 8; 5 on September 9 – 11, and 12, 15, 12, and 8 on September 12 – 15.

Look for comments from readers concerning the transition from summer to fall conditions in Friday’s bulletin.

Sunspot numbers for August 10 through 16, 2023, were 83, 105, 61, 89, 85, 107, and 140, with a mean of 95.7. The 10.7-centimeter flux was 155.7, 152.8, 148.3, 150.4, 154, 158.1, and 160.1, with a mean of 154.2. Estimated planetary A indices were 7, 5, 8, 5, 5, 5, 5, 5, 5, 4, and 8, with a mean of 6. The middle latitude A index was 8, 6, 10, 7, 6, 7, and 10, with a mean of 7.7.

A comprehensive Solar Update is posted Fridays on the ARRL website. For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…,” and check out the Propagation Page of Carl Luetzelschwab, K9LA.

A propagation bulletin archive is available. For customizable propagation charts, visit the VOACAP Online for Ham Radio website.

Share your reports and observations.

A weekly, full report is posted on ARRL News.

Two new sunspot groups appeared on August 3, and then three more appeared on August 7, followed by another on August 9.

But solar activity was lower during our current reporting week of August 3 – 9, with the average daily sunspot number dropping from 154.3 to 108.9, and average solar flux from 173 to 166.4.

The average daily planetary A index rose from 8.3 to 12.3, and the average middle latitude A index rose from 9.3 to 10.1.

The middle latitude A index on August 3 – 4 was not available, so I estimated the value based on the planetary A index and remaining five middle latitude readings for the rest of the week.

Predicted solar flux is 150 on August 10 – 12; 145, 140, 130, and 135 on August 13 – 16; 162 on August 17 – 18; 164 on August 19 – 20; 168 on August 21 – 23; 172, 172, and 170 on August 24 – 26; 172, 172, and 174 on August 27 – 29; 172, 172, and 170 on August 30 – September 1; 168, 168, 166, and 164 on September 2 – 5, and 162, 162, 164, and 164 on September 6 – 9.

Predicted planetary A index is 12 on August 10; 5 on August 11 – 14; 12 and 8 on August 15 – 16; 5 on August 17 – 25; 12 on August 26, and 5 on August 27 – September 4.

On August 9, Spaceweather.com wrote about a 1940 geomagnetic storm that sounds similar to the infamous Carrington Event.

Two coronal mass ejections hit Earth, each 109 minutes apart. Read a recent scientific paper on the event at https://bit.ly/3s1VrMh.

Check out the following articles on solar flares:

https://bit.ly/3KXlUl1

https://bit.ly/3qj0pE6

https://bit.ly/3QPYPV9

https://bit.ly/45naVsF

Space weather forecaster Dr. Tamitha Skov, WX6SWW, recently uploaded this video:

https://youtu.be/Olfjss8GmSI Sunspot numbers for August 3 – 9, 2023, were 124, 122, 100, 97, 101, 115, and 103, with a mean of 108.9. The 10.7-centimeter flux was 162.9, 170.8, 175.8, 173.5, 169.7, 158.9, and 153.4, with a mean of 166.4. Estimated planetary A indices were 6, 13, 36, 4, 12, 8, and 7, with a mean of 12.3. Middle latitude A index was 5, 12, 24, 4, 11, 7, and 8, with a mean of 10.1.

The Australian Space Weather Forecasting Centre issued a geomagnetic disturbance warning at 0233 UTC on August 3, 2023:

“Two recent coronal mass ejections (CMEs) are expected to impact Earth on UT day 05-Aug, with the second possibly arriving early 06-Aug. G0-G1 geomagnetic conditions may be expected on 05-Aug, with a chance for isolated periods of G2 towards the end of the UT day on 05-Aug. Geomagnetic storm conditions may persist over 06-Aug.”

Solar activity was up during this reporting week, July 27 through August 2.

Average daily sunspot numbers increased from 128.1 to 154.3, but the average daily solar flux was about the same as last week, moving from 172.2 to 173.

Geomagnetic indicators were quiet, with the average daily planetary A index shifting from 11 to 8.3, while middle latitude numbers went from 11.1 to 9.3.

Predicted solar flux is 170 and 165 on August 3 – 4; 160 on August 5 – 7; 155, 145, and 168 on August 8 – 10; 168 on August 11 – 12; 170 on August 13 – 16; 172 on August 17 – 18; 170 and 168 on August 19 – 20; 170 on August 21 – 22; 172 on August 23; 170 on August 24 – 27, and 165 on August 28 – 31.

Predicted planetary A index is 10, 20, 28, 15, and 8 on August 3 – 7; 5, 5, and 10 on August 8 – 10; 8 on August 11 – 12; 5 on August 13 – 25; 12 and 10 on August 26 – 27, and 5 on August 28 – 31.

ARRL published an excellent new book, Here to There: Radio Wave Propagation, written by a team of experts, including Frank Donovan, W3LPL; Nathaniel Frissell, W2NAF, and Carl Luetzelschwab, K9LA. It’s a great reference on all aspects of HF and VHF propagation and it includes a survey of the various propagation prediction computer programs.

Sunspot numbers for July 27 through August 2 were 154, 148, 147, 139, 197, 160, and 135, with a mean of 154.3. The 10.7-centimeter flux was 165.3, 168.2, 178.6, 174.4, 177.1, 174.7, and 172.9, with a mean of 173. Estimated planetary A indices were 7, 6, 9, 9, 6, 9, and 12, with a mean of 8.3. Middle latitude A index was 7, 5, 8, 18, 8, 9, and 10, with a mean of 9.3.

Average daily sunspot numbers declined from 130.6 to 128.1 over the past week of July 20 – 26.

Average daily solar flux declined significantly from 190.5 to 172.2.

The solar flux forecast sees values at 168, 165, and 162 on July 27 – 29; 158 on July 30 – 31; 155 and 158 on August 1 – 2; 165 on August 3 – 4; 170 and 175 on August 5 – 6; 180 on August 7 – 10; 175 on August 11 – 13; 180 on August 14 – 15; 175 on August 16 – 18; 170 on August 19; 165, 165, and 160 on August 20 – 22, and 155 on August 23 – 26.

Predicted planetary A index is 20, 10, 5, 10, and 8 on July 27 – 31; 5, 5, 10, and 8 on August 1 – 4; 5 on August 5 – 9; 10 on August 10; 8 on August 11 – 13; 5 on August 14 – 19, and 10, 8, and 5 on August 20 – 22.

Read about sunspots, flares, and aurora at the following link:

https://bit.ly/44JxcRp

Check out a story about the Mars rover seeing the far side of the sun at the link below:

https://bit.ly/3KbRV8b

Also, see the report of a rocket punching a hole in the ionosphere at:

https://bit.ly/3KceBFB

Nearly 5 decades ago in Marin County, California, I, too, witnessed a rocket penetrating the ionosphere. It was a huge, dramatic display. My friend had seen a similar thing before, and said it was created by a rocket launch from Vandenberg Air Force Base in Southern California.

Sunspot numbers for July 20 – 26, 2023, were 131, 121, 103, 117, 141, 137, and 147, with a mean of 128.1. The 10.7-centimeter flux was 184.3, 172.8, 174.4, 172.5, 165.1, 169, and 167.4, with a mean of 172.2. Estimated planetary A indices were 10, 13, 9, 6, 7, 11, and 21, with a mean of 11. Middle latitude A index was 10, 11, 9, 5, 8, 12, and 23, with a mean of 11.1.

Average daily sunspot numbers declined, but the average daily solar flux increased. Sunspot averages were 181.9 last week and 130.6 this week. The average daily solar flux increased from 179.4 to 190.5.

Two new sunspot groups emerged on July 14, as well as three more on July 17, and another two on July 19.

The average daily planetary and middle latitude A indices were both 12.9 this week, rising from 8.6 and 8.1.

Predicted solar flux is 188 on July 20 – 23; 186, 184, 186, and 160 on July 24 – 27; 165 on July 28 – 29; 170 on July 30 – 31; 165 on August 1 – 4; 170, 175, 175, and 170 on August 5 – 8; 165 on August 9 – 11; 170 on August 12; 175 on August 13 – 14, and 170 on August 15 – 19.

The predicted planetary A index is 28, 20, and 12 on July 20 – 22; 5 on July 23 through August 2; 10 and 8 on August 3 – 4; 5 on August 5 – 14, then 12, 8, and 8 on August 15 – 17.

CNN presented a smart piece on the sunspot cycle peaking sooner than expected:

https://bit.ly/3rzNJJ6

Cosmos published an article about a double-peaked solar flare:

https://bit.ly/46ZoznE

Sunspot numbers for July 13 – 19, 2023, were 146, 141, 96, 99, 149, 142, and 141, with a mean of 130.6. The 10.7-centimeter flux was 202.9, 180.6, 178.5, 184.3, 180, 218.5, and 188.9, with a mean of 190.5. Estimated planetary A indices were 7, 20, 8, 10, 24, 16, and 5, with a mean of 12.9. Middle latitude A index was 9, 17, 9, 13, 19, 16, and 7, with a mean of 12.9.

Solar Update is posted Fridays on the ARRL website. For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…,” and check out the Propagation Page of Carl Luetzelschwab, K9LA.

A propagation bulletin archive is available. For customizable propagation charts, visit the VOACAP Online for Ham Radio website.

Share your reports and observations.